1. Field of the Invention
The present invention relates to an optical information recording/reproducing apparatus such as an optical disk apparatus, a magnetooptical disk apparatus, and the like and, more particularly, to an apparatus providing a reduction of power consumption upon execution of focusing or tracking servo control of the information recording/reproducing apparatus.
2. Related Background Art
Conventionally, an objective lens driving device for an optical disk apparatus is normally constituted by two units, i.e., a lens actuator unit for driving an objective lens within the near-distance range, and a linear motor unit for moving the lens actuator unit over the entire track area.
However, in recent years, in order to attain a high-speed access to an information track, a lightweight objective lens driving device has been proposed. Japanese Laid-Open Patent Application No. 5-298724 discloses such an objective lens driving device. FIGS. 1 and 2 show the objective lens driving device disclosed in Japanese Laid-Open Patent Application No. 5-298724. The objective lens driving device (to be simply referred to as an actuator hereinafter) shown in FIGS. 1 and 2 is arranged in such a manner that an objective lens is supported by a leaf spring, and can be moved in the tracking direction over the entire track area upon deflection of the leaf spring.
Referring to FIGS. 1 and 2, an objective lens 1A irradiates a recording/reproducing spot onto the surface of an optical disk. A holder 2 is arranged in a fixed optical head unit (not shown), and holds a pop-up mirror for deflecting a laser beam emitted by a light source toward the objective lens. Inner yokes 10 extend in a direction parallel to the tracking direction, and extend through the centers of tracking coils 13. An outer yoke 12 extends parallel to each inner yoke 10, and is coupled thereto at its two end portions. A magnet 11 is attached to each outer yoke 12, and constitutes a magnetic circuit for applying a magnetic flux in a direction perpendicular to each coil 13. Note that a focusing coil 14 is arranged on the holder 2.
A parallel leaf spring member has the following arrangement. A fixed base member 4A is fixed to one outer yoke 12. Leaf springs 4B are connected to the fixed base member 4A. A movable frame member 4C is connected to the end portions, opposite to the member 4A, of the leaf springs 4B. Leaf springs 4D are connected to the movable frame member 4C. The objective lens holder 2 is connected to the end portions, opposite to the member 4C, of the leaf springs 4D. With this arrangement, when the actuator is driven, the movable frame member 4C moves in an arcuated pattern since the leaf springs 4B are deflected. At the same time, since the leaf springs 4D are deflected, the objective lens holder 2 moves along a linear path. FIG. 2 shows the state of the objective lens driving device when the leaf springs are deflected. The objective lens holder 2 is driven by the magnetic circuit, and are moved along the inner yokes 10. At this time, the parallel leaf spring member allows movement in the tracking direction upon bending of the leaf spring 4B while supporting the objective lens holder 2. Thus, the objective lens driving device does not require the two-unit arrangement, and the movable portion mass of the objective lens driving device can be greatly reduced.
Since the objective lens holder 2 is supported by the springs, when the objective lens holder 2 is located at a position other than the neutral position of the springs, a spring force for carrying the objective lens holder 2 to the neutral position of the springs is generated. Therefore, when the objective lens holder 2 is to be held at a position other than the neutral position of the springs, a current must be kept supplied to the coils to generate a driving force against the spring force.
In a recording/reproducing apparatus such as an optical disk apparatus, when recording or reproduction is not performed, the irradiation point of the beam spot is held at the last position of the recording or reproduction.
FIG. 3 is a flow chart showing the operation of the conventional optical disk apparatus. Referring to FIG. 3, when the optical disk apparatus is activated (step 901), the control executes a loop consisting of wait jump processing (step 902), recording discrimination branch processing (step 903), and reproduction discrimination branch processing (step 904), and waits for a recording or reproducing order from a system controller while executing wait jump processing. Upon reception of a recording or reproducing order, the control moves the irradiation point of the beam spot to a predetermined address (step 905) or (step 907), and performs a recording or reproduction operation (step 906) or (step 908). Upon completion of the recording or reproduction operation, the control waits for an order from the system controller while executing a wait operation at the end position of the recording or reproduction operation.
In the conventional optical disk apparatus, the wait jump processing is performed as follows. An optical disk normally has spiral tracks. For this reason, when the beam spot position is controlled to trace a track, the beam spot moves to an unexpected position along the spiral tracks. In order to hold the irradiation position of the beam spot at a predetermined position, the beam spot is jumped to be returned by one track per revolution of the disk. With this operation, the beam spot can be held at the desired position on the disk.
However, in order to hold the irradiation position of the beam spot at the last recorded or reproduced position using the above-mentioned spring-supported actuator, the actuator requires a driving force against the spring force of the springs, and a current must be kept supplied to the coils, resulting in a large power consumption of the apparatus. In particular, except for a case wherein the focusing or tracking servo time matches the recording or reproducing time, electric power consumed by the servo control is not effective.